Browsing by Author "Chu, Tien-Min Gabriel"

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    The antimicrobial efficacy of innovative 3D triple antibiotic paste-mimic tubular scaffold against actinomyces naeslundii
    (2015) Azabi, Asma Abulqasem; Bottino, Marco C.; Gregory, Richard L.; Spolnik, Kenneth J.; Cook, Norman Blaine, 1954-; Chu, Tien-Min Gabriel
    Background: Root canal disinfection is an essential requirement for the success of regenerative endodontics. Currently, the so-called triple antibiotic paste (TAP) is considered the standard of care. Notwithstanding the good antimicrobial capacity, the high concentration of TAP has shown significant toxicity to human cells, especially dental pulp stem cells. A novel drug release system, i.e., a triple antibiotic paste-mimic electrospun scaffold containing low concentrations of the antibiotics present in the TAP, has emerged as an effective and reliable alternative to fight root canal infections without potential toxic effects on dental stem cells, which are an integral part of the regenerative treatment. Objectives: The aim of this study was to determine the antimicrobial efficacy of an innovative three-dimensional (3D) triple antibiotic paste-mimic tubular scaffold against Actinomyces naeslundii biofilm formed inside human root canal dentinal tubules. Materials and methods: Pure polydioxanone (PDS) polymer solution and PDS loaded with metronidazole, ciprofloxacin and minocycline (35 wt.% of each antibiotic, 3D-TAP-mimic scaffold) were spun into 3D fibrous scaffolds. A. naeslundii (ATCC 43146) was centrifuged to induce biofilm formation inside human root canal dentinal tubules using a dentin slice model (1 mm thickness and 2.5 mm canal diameter). The infected dentin slices were exposed to the 3D-TAP-mimic scaffold, TAP solution (50 mg/mL of each antibiotic), and antibiotic-free PDS. Biofilm elimination was quantitatively and qualitatively analyzed by confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM), respectively. Results: A dense penetration of A. naeslundii biofilm was observed by CLSM throughout the dentinal tubules. 3D-TAP-mimic scaffold significantly reduced the percentage of viable bacteria compared with PDS (p <.05). TAP solution completely eliminated viable bacteria without differing from 3D-TAP-mimic scaffolds. SEM images showed results similar to CLSM. Conclusion: Collectively, the proposed tubular 3D-TAP-mimic scaffold holds significant clinical potential for root canal disinfection strategy prior to regenerative endodontics.
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    Benchside to Bedside: The Launching of a Novel Bone Healing Agent
    (Office of the Vice Chancellor for Research, 2013-04-05) Bemenderfer, Thomas; Busenbark, John; Kansal, Jagan; Chu, Tien-Min Gabriel; Kacena, Melissa A.
    The ability to evolve a nascent idea into a successful entity requires navigation through a number of perils known to debilitate new ventures. Embryonic firms (or ideas) require sufficient development; from establishing an unambiguous approach, to attaining the necessary capital for evolution and growth, to fostering an environment and market for the idea or product. In the venture community, there are a number of advocates who possess the ability to contribute to new ventures (e.g. venture community support functions, venture capitalists, or informal contributors), and these individuals help navigate the startup or idea through inception to effectuation. Academic faculty, though, who often are not engrained into the local venture community, are frequently disadvantaged because their ideas or new firms come as an ancillary to their primary work. Already potentially impeded by the challenges presented by the legal constraints of providing sufficient equity for ideas to the university, developing a clear, effective path to market can be difficult for academic faculty. In addition to the systemic uncertainty, difficulty, and impediments faced by all entrepreneurs, academic faculty are constrained by limited time, funding, experience, and other resources – all related to their inclusion in the university or system. In order to alleviate these constraints and propel cutting-edge scientific breakthroughs and technological development, Innovation-to-Enterprise Central (ITEC) was initiated to assist academic faculties’ developments into the market – where, ultimately, these products will have the greatest utility to society. Osetofuse is an embryonic firm in the nascent stages of conceptualizing a revolutionary new product, which uses thrombopoietin as a novel bone healing agent. Through the ITEC program, Osteofuse has been able to facilitate the exploration of the potential value (clinically, economically, and societally) of its research and how the initial idea can be developed into a commercialized and monetized product. In the process, it has developed mechanisms to gauge the market’s acceptance of the product, the intellectual property and legal issue constraints facing the idea, potential commercialization streams and related valuations for marketization, and a quantitative analysis of projected revenue provisions. ITEC fosters continual compounding of knowledge capacity, as the trajectory of Osteofuse has not only inclined, but redirected because of specific uncovered data and insight from the program. As a result, Osteofuse has undergone dramatic transformation; in terms of both its formal identity and the potential approach to the market.
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    Biomechanical and histological evaluation of a new zirconia implant in a canine model
    (2015) Hamada, Yusuke; Chu, Tien-Min Gabriel; Prakasam, Sivaraman; Zunt, Susan L.; Liu, Sean Shih-Yao; Blanchard, Steven
    Background: Currently titanium implant fixtures are considered as a gold standard because of their biocompatibility and their clinical success rates have been well documented. The esthetic outcome of restorations supported by titanium implants may be compromised if the dark gray color of the implant shows through a thin peri-implant mucosa or if the implant fixture becomes visible following soft tissue recession. Also titanium might cause allergic reactions. For these reasons, zirconia implants have been considered as alternative materials because of their white color, high material properties and biocompatibilities. Still, further investigations are necessary to confirm the in-vivo performance of these implants. Purpose: The purpose of this study is to determine the histomorphometric and biomechanical properties of zirconia implants manufactured by Shofu Inc. with a sand-blasted and acid-etched surface treatment, compared to that of the titanium implants from the same manufacturer with a sand-blasted and acid-etched surface treatment in a canine model. Material and Methods: Six beagle dogs (1-2 years old) will be used in this split mouth trial. After 8 weeks following extraction of the second to fourth mandibular premolars, zirconia implants (experimental group) and titanium implants (control group) were placed on the each side of mandible. At 8 weeks and 12 weeks after implant placement, the animals were sacrificed, and implants were removed in block sections, and histological and histomorphometric analyses were measured. Specifically, the bone-implant contact (BIC), bone area (BA), removal torque (RTQ), mineral apposition rate (MAR), bone forming area (BFA), and Periotest value (PTV) of the two groups were studied and compared. Results: At 12 weeks post operatively, one Shofu thread type Ti implant were not integrated. Over all failure implant was 0/12 in zirconia group, and 1/12 in titanium group. In 8 weeks samples, only statistical differences were higher BA (p=0.02) in macro threads area and BFA (p=0.02) in zirconia implants group than titanium implants group. In 12 weeks group, zirconia implant group showed higher MAR at 9-10 and 10-11weeks time frame (p=0.02, and 0.04 restectively), and PVT value (p=0.01) than titanium implants group. Removal torque value increased in both titanium and zirconia group with time. Average of removal torque value showed higher in titanium implants than zirconia implants, but the differences were not statistically significant in both 8 weeks (Ti; 64.16±16.93 N-cm, ZrO₂: 42.5±6.01 N-cm : p=0.247) and 12 weeks (Ti; 82.5±9.41 N-cm, ZrO₂: 51.3±19.38 N-cm: p=0.16). In the removal torque analysis, it is observed that the bone-implant interface seems to be of more rigid and brittle in nature as indicated by the lower averaged onset angle, peak angle, area under curve and RTQ. Conclusion: Zirconia implants group showed higher value of BA with macro thread and BFA in 8weeks and MAR at 9-10, 10-11 weeks period, and PVT in 12 weeks post operatively. Within the limited number of samples tested in this study, there is no difference between the BIC and RTQ of zirconia and titanium implants after 8 and 12 weeks of implantation.
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    Bond strength evaluation of two resin cements with two adhesives and analysis of mode of failure
    (2009) Mohan, Preethi; Platt, Jeffrey A.; Chu, Tien-Min Gabriel; Moore, B. Keith; Taskonak, Burak; Matis, Bruce A.; Cochran, Michael A.
    Cementing of indirect restorations with resin cements generally requires the pre-treatment of dentin with an adhesive. When dual-cured or chemical-cured resin cements are used with these single-step adhesives, incompatibility issues exist. This has resulted in manufacturers making chemical changes in their products. Kerr Dental markets a new resin cement, Nexus Third generation (NX3), which utilizes a proprietary redox system different from the second generation of composite luting agent (NX2). The aim of this study was to evaluate microtensile bond strength and mode of failure of NX3 and NX2 with two different adhesive systems (total-etch and self-etch) after 1 week and after 3 months of storage. Methods: Sixty-four non-carious teeth were sectioned to expose the dentin using a low-speed saw. Dentin surfaces were ground with 320-grit SiC paper. The adhesives Optibond Solo Plus (SOL), and Optibond All In One (AIO) were applied, and resin cements (NX2, NX3) were used to lute 4-mm composite discs to the treated dentin surfaces. Microtensile bond strength was determined at 1 week (IM) and after 3 months (3MON) of storage using a universal testing machine (MTS). All specimens were examined under the stereomicroscope to determine the mode of failure. Random specimens from each failure group were examined using scanning electron microscopy. Statistical Analysis: Comparisons between the treatment combinations for differences in microtensile bond strength were performed using Weibull-distribution survival analysis. Comparisons between the treatment combinations for differences in the failure mode were performed using Fisher’s Exact tests. The group NX3 SOL IM (30.5 MPa) had significantly higher bond strength than NX3 SOL 3MON (13.4 MPa); NX3 AIO IM (11.3MPa); NX3 AIO 3MON (8.2 MPa; NX2 AIO 3MON (5.8 MPa); NX2 SOL IM (6.3 MPa), and NX2 SOL 3MON (3.2 MPa). The group NX2 AIO IM (19.3 MPa) was not significantly different from NX3 SOL IM. The group NX2 SOL 3MON and group NX2 SOL IM had a significantly higher percentage of teeth with mixed failure than all of the other groups. None of the other groups had significantly different failure mode. The group NX3 SOL IM had 90-percent beam survival beyond 17 MPa, and NX2 AIO IM had 50 percent of beams surviving beyond 17 MPa, a better performance. For all the other groups, more than 50 percent of beams failed below 17 MPa. Results show high evidence of degradation for all groups considered in this investigation. The use of these types of cement adhesive combinations in clinical situations should be used with this understanding.
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    Bone regeneration in novel porous titanium implants
    (2010) Khouja, Naseeba, 1981-; Chu, Tien-Min Gabriel; Brown, David T.; Platt, Jeffery A., 1958-; Blanchard, Steven B.; Levon, John A.
    The objective of this study was to evaluate the in vivo performance of the novel press-fit dental implant fabricated via electron beam melting (EBM, Southern Methodist Univ.) and compare it to a commercially-available porous-coated press-fit dental implant (Endopore, Innova Corp.). Twelve cylindrical shaped implants 3 mm in diameter x 5 mm long were made by EBM (Southern Methodist Univ.) using Ti6Al4V ELI alloy. Twelve commercial implants (Endopore, Innova Corp.) of the same geometry were used as controls. Samples were implanted in rabbit tibia and retrieved six weeks postoperatively. Six specimens from each implant type were embedded undecalcified, sectioned, and stained with toluidine blue (Sigma) for histomorphometry analysis. Bone-to-implant contact (BIC) was measured. On the six remaining samples from each implant type, the mechanical properties were evaluated by pushout test on a material testing machine. The samples were loaded at a loading rate of 1 mm/min. The pushout strength was measured and the apparent shear stiffness was calculated. The results were analyzed with a paired-t test. The histology shows osteointegration of surrounding bone with both implant types. Bone was found to grow into the porous space between the beads. Both the Endopore (Innova Corp.) and the EBM (Southern Methodist Univ.) showed similar BIC. The mean BIC for the Endopore (Innova Corp.) and EBM (Southern Methodist Univ.) implant were 35 ± 6% and 32 ± 9%, respectively. It failed to reach statistical significance (p > 0.05). The peak pushout force for Endopore (Innova Corp.) and EBM (Southern Methodist Univ.) implants were 198.80 ± 61.29 N and 243.21 ± 69.75 N, respectively. The apparent shear stiffness between bone and implant for the Endopore (Innova Corp.) and EBM (Southern Methodist Univ.) implants were 577.36 ± 129.99 N/mm; and 584.48 ± 146.63 N/mm, respectively. Neither the peak pushout force nor the apparent shear stiffness of the implants was statistically different between the two groups (p > 0.05). The results suggest that the implants manufactured by EBM (Southern Methodist Univ.) perform equally well as the commercial implant Endopore (Innova Corp.) in this current animal model.
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    Compromised Osseous Healing of Dental Extraction Sites in Zoledronic Acid-Treated Dogs
    (2011-02) Allen, Matthew R.; Kubek, Daniel J; Burr, David B.; Ruggiero, Salvatore L; Chu, Tien-Min Gabriel
    Summary The goal of this study was to document how treatment with high doses of zoledronic acid affects dental extraction healing. Our results, showing significantly compromised osseous healing within the socket as well as presence of exposed bone and development of a sequestrum in one animal, provide a building block toward understanding osteonecrosis of the jaw. Purpose The goal of this study was to document how treatment with a bisphosphonate affects the bone tissue following dental extraction. Methods Skeletally mature female beagle dogs were either untreated controls (CON) or treated with intravenous zoledronic acid (ZOL). Following the extraction of the fourth premolars, healing was allowed for 4 or 8 weeks. Properties of the extraction site were assessed using microcomputed tomography (micro-CT) and dynamic histomorphometry. Results The initial infilling of the extraction socket with bone was not affected by ZOL, but subsequent removal of this bone was significantly suppressed compared to CON. After 8 weeks of healing, the alveolar cortical bone adjacent to the extraction socket had a remodeling rate of ∼50% per year in CON animals while ZOL-treated animals had a rate of <1% per year. One ZOL-treated animal developed exposed bone post-extraction which eventually led to the formation of a sequestrum. Assessment of the sequestrum with micro-CT and histology showed that it had features consistent with those reported in humans with osteonecrosis of the jaw. Conclusions These results, showing significantly compromised post-extraction osseous healing as well as presence of exposed bone and development of a sequestrum in one ZOL animal, provide a building block toward understanding the pathophysiology of osteonecrosis of the jaw.
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    The effect of acid etching on remineralization of incipient caries lesions : a micro-ct study
    (2009) Yeslam, Hanin E.; Ando, Masatoshi; Gonzalez-Cabezas, Carlos, 1966-; Chu, Tien-Min Gabriel; Lund, Melvin; Cochran, Michael
    Etching of enamel caries lesions has been demonstrated to enhance remineralization. However, this effect reaches a plateau after a period of time. This study aimed at investigating the effectiveness of additional acid etching on remineralization. Forty 1 mm × 2 mm human enamel blocks with chemically induced artificial incipient lesions were used. Ten specimens were randomly selected at the end of demineralization for transverse microradiography (TMR) analysis. The remaining specimens were then divided into three groups (n = 10). Group A was remineralized by a pH cycling system with 1100 ppm sodium fluoride for 20 days. In group B, the specimens were etched with 35-percent phosphoric acid for 30 s and then remineralized. Group C was remineralized by same procedure as group B plus and given an additional acid etch after 10 days of remineralization. Mineral density was measured by x-ray microtomography (µ-CT). The volumetric mineral content [VM (µm3×105)] was determined between 91 and 0-wt%. The µ-CT % mineral recovery (%) was calculated using the formula 100×(remineralize VM - demineralization VM) / (sound VM - demineralization VM). One-hundred-μm sections of demineralized and remineralized specimens were used to assess the mineral loss (IML: vol%×µm) and lesion depth (µm) using TMR. The three groups showed no significant difference in mineral change or mineral content for µ-CT or TMR lesion depth. The TMR IML showed a significant difference between the demineralized specimens and the three remineralized groups. The correlation between TMR IML and TMR lesion depth was 0.66 (p < 0.0001). The µ-CT percent mineral recovery from demineralization was correlated with neither TMR IML nor TMR lesion depth. When evaluated with µ-CT, the twice-acid-etched group presented lower mineral gain values than the group etched only once with acid. Also, the twice-etched group presented lower mineral gain and greater TMR IML compared with the non-acid etch group. TMR images revealed reduction of surface layer in the acid-etched groups, especially in the twice-etched group, in which significant reduction or loss of surface layer occurred. Based on these results, we conclude that additional acid etching with 35-percent phosphoric acid does not enhance remineralization compared with a single application of acid etching. We believe that the viable existence of the surface layer is essential for remineralization of the lesion. Further investigations into the accuracy of µ-CT to detect minute mineral changes in incipient caries lesions are probably needed.
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    The effect of endodontic regeneration medicaments on mechanical properties of radicular dentin
    (2013) Yassen, Ghaeth H.; Platt, Jeffrey A., 1958-; Chu, Tien-Min Gabriel; Murray, Peter E.; Allen, Matthew R.; Vail, Mychel Macapagal, 1969-
    Endodontic regeneration treatment of necrotic immature teeth has gained popularity in recent years. The approach suggests a biological alternative to induce a continuous root development. In this project, three in vitro experiments were conducted to investigate the effect of three medicaments used in endodontic regeneration on mechanical properties and chemical structure of radicular dentin. In the first experiment, we investigated longitudinally the effect of medicaments on the indentation properties of the root canal surface of immature teeth using a novel BioDent reference point indenter. A significant difference in the majority of indentation parameters between all groups was found after one-week and one-month application of medicaments (p<0.0001): triple antibiotic paste (TAP) > double antibiotic paste (DAP) > control > calcium hydroxide [Ca(OH)2]. The four-week exposure of dentin to TAP and DAP caused 43% and 31% increase in total indentation distance outcome, respectively. In the second experiment, we investigated longitudinally the effect of medicaments on the chemical structure of immature radicular dentin by measuring the phosphate/amide I ratios of dentin using Attenuated Total Reflection Fourier Transform Infrared Spectroscopy. Phosphate/amide I ratios were significantly different between the four groups after one week, two weeks and four week application of medicaments (p<0.0001): Ca(OH)2-treated dentin > untreated dentin > DAP-treated dentin > TAP-treated dentin. In the third experiment, we investigated longitudinally the effect of medicaments on root fracture resistance and microhardness of radicular dentin. For the microhardness, the two-way interaction between group and time was significant (p<0.001). TAP and DAP caused a significant and continuous decrease in dentin microhardness after one and three month application, respectively. The three-month intracanal application of Ca(OH)2 significantly increased the microhardness of root dentin. The time factor had a significant effect on fracture resistance (p<0.001). All medicaments caused significant decrease in fracture resistance ranging between 19%-30% after three month application compared to one week application. The three medicaments used in endodontic regeneration caused significant change in the chemical integrity of the superficial radicular dentin and significantly affected the indentation properties of the root canal surface. Furthermore, the three month intracanal application of medicaments significantly reduced the fracture resistance of roots.
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    The effect of filler on the mechanical properties of a novel resin-based calcium phosphate cement
    (2010) Al Dehailan, Laila; Chu, Tien-Min Gabriel; Lund, Melvin R, 1922-; Cochran, Michael A. (Michael Alan), 1944-; Martinez Mier, Esperanza de los A. (Esperanza de los Angeles), 1967-; Cook, Norman Blaine, 1954-
    Several studies have found that resin-based amorphous calcium phosphate (ACP) composites can function well for applications that do not require high mechanical demand. Milled tricalcium phosphate (TCP), a new calcium-phosphate-releasing material, is crystalline in nature, suggesting it to be strong. In the present study, we investigated the use of a TCP-filled composite resin as a possible tooth restorative-material. An experimental TCP-based composite was prepared using monomer with a mixture of 34.3 percent by mass of EBPADMA, 34.2 percent by mass of HmDMA, and 30.5 percent by mass of HEMA. TCP fillers were added to the monomer mixture at different levels (30 percent, 40 percent, 50 percent, and 60 percent by weight). A universal testing machine (Sintech Renew 1121; Instron Engineering Corp., Canton, MA) was used to measure the compressive strength and modulus. FTIR was used to measure the degree of conversion. The depth of cure was determined according to the ISO standards for dental resin 4049 using the scrapping technique. Knoop hardness numbers were obtained by a microhardness tester (M-400; Leco Co., St. Joseph, MI). The viscosities of the experimental resin were determined in a viscometer (DV-II+ Viscometer; Brookfield, Middleboro, MA). The data were analyzed using a one-way analysis of variance (ANOVA). A 5-percent significance level was used for all the tests. Resin composites with 30-percent TCP filler showed the highest compressive strength and hardness values. Also, this group showed the lowest degree of conversion. Resin composites with 60-percent TCP filler showed the highest degree of conversion. However, this group showed the lowest compressive strength, depth of cure, and hardness. Resin composites with 50-percent filler showed the highest compressive modulus. Resin composites with 40-percent filler showed higher viscosity values than resin composites with 30-percent filler. In conclusion, increasing the filler level significantly reduced the compressive strength, hardness, and depth of cure, but increased the degree of conversion. Also, resin composites with the lowest filler level (30 percent) had the highest compressive strength, depth of cure, and hardness. From these results, it can be concluded that the experimental TCP-filled resin used in this study cannot be used as restorative material.
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    Effect of fluoride and abrasives on artificial enamel caries lesions
    (2012) Nassar, Hani M., 1979-; Hara, Anderson T.; González-Cabezas, Carlos, 1966-; Lippert, Frank; Fontana, Margherita Ruth, 1966-; Chu, Tien-Min Gabriel
    Hypothesis: The interaction between the abrasive level and fluoride concentration of dentifrice slurries modulates the surface loss (SL) and remineralization of incipient enamel caries (IEC). Methods: Three types of IEC were created and six experimental slurries with different combinations of fluoride content and abrasive level were tested. In experiment 1, the three IEC were subjected to brushing (with experimental slurries) and remineralization cycles for 5 days. Fluoride concentrations (0 and 275 ppm as NaF) and abrasive levels (Low and High) were tested. SL was determined by optical profilometry at baseline and after 1, 3, and 5 days. In experiment 2, changes in IEC mineral content (Δ(ΔZ)C) and depth (ΔLC) were investigated at baseline and after the 5-day cycling with transverse microradiography. In experiments 3 and 4, SL of MeC and CMC lesions were further studied, respectively; testing not only fluoride concentration (275 and 1250 ppm as NaF) and abrasivity (low and high) of the slurry, but also the brushing frequency (1x, 2x, and 3x/day). Brushing-remineralization cycles were performed for 7 days. Statistical analyses were performed at 5% significance level. Results: Experiment 1: overall, brushing with the high-abrasive slurry caused more SL than with the low-abrasive. For CMC and MeC lesions, 0 ppm F had more SL than 275 ppm F only after day 3. Fluoride had no effect on the SL of HEC lesions. Experiment 2: fluoride and abrasives did not have a significant effect on IEC. HEC had significantly lower Δ(ΔZ)C than CMC and MeC, with CMC and MeC not differing from each other. Lesion type had no effect on ΔLC. Experiment 3: brushing CMC lesions 3x/day with 1250 ppm F increased SL compared to 1x/day, after 5 and 7 days. Study 4: brushing MeC lesions with high abrasive slurry containing 1250 ppm F increased SL after 5 and 7 days. Conclusions: The IEC tested showed different SL and remineralization behaviors. The fluoride content and abrasive level of the toothpaste showed to be relevant modulating the SL of enamel caries lesions as well as their remineralization behavior.